


Compulsive Instincts

by paintstroke



Category: Voltron: Legendary Defender
Genre: Alpha/Alpha, Alpha/Beta/Omega Dynamics, Anal Sex, Enthusiastic Consent, Established Relationship, Knotting, M/M, SHEITH - Freeform, Sparring
Language: English
Status: Completed
Published: 2018-01-05
Updated: 2018-01-05
Packaged: 2019-02-28 17:55:32
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,001
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13276812
Author URL: https://archiveofourown.org/users/paintstroke/pseuds/paintstroke
Summary: (Sheith) Alpha/Alpha. The scent of an omega going into heat nearly sends Shiro into a rut, but Keith thinks he can use that to get what he wants...





	Compulsive Instincts

**Author's Note:**

> A/N: This was me trying to see what sort of sexy stories I could fit into a 3K wordcount as practice for a zine submission. :) Apologies (well, maybe? unless it's your thing, in which case, hopefully you can enjoy!), the start of 2018 is going to be heavy on omegaverse plot-bunnies from me. 
> 
> Also I know there's a lot of fandom drift for Keith's character... for this story I've jumped into that current (and it was fun).

* * *

Keith wrinkled his nose, bringing a hand up to try to breathe through it. An alien scent was thick in the air, out of place in the usually bland and sterile Castle. It was cloying; sparking vague memories of heavy perfumes. He sucked air through his teeth in an attempt to avoid smelling it. He ended up trying to scrape remnants of the air from his tongue using the roof of his mouth, twisting his face in disgust. 

Keith looked over his shoulder at Shiro, about to suggest that they find another wing to train in. This whole hallway was foul; there was no guarantee the training room would be any better. 

If he hadn’t seen Shiro’s eyes darken he might not have detected the scent underneath the perfume. Keith caught his breath as he watched his boyfriend fight against the instincts the pheromones called to.

Someone had gone into heat. 

Keith sniffed again, out of a vague sense of curiosity, but the perfume masked almost all traces of who it might be. Then again, he hadn’t really primed himself to be as sensitive to omega pheromones as other alphas were. He just wasn’t attracted to them, not like he’d been told he should be. 

“Keith…” Shiro grimaced and rubbed the bridge of his nose. 

“Yeah. I smell it too,” Keith confirmed, distracted by the blush rising under Shiro’s fingers, his scar paling against the heated skin. 

Shiro was still for a moment or two, eyes unfocused as he contemplated the omegas isolating themselves in comforting nests. Keith’s eyebrows knit together and he stroked his hand over Shiro’s bicep. “We should go,” he prompted Shiro. “We can train in another wing of the Castle… with that perfume I can’t tell where they went, best to just clear out of here.”

Shiro didn’t move though, so Keith moved himself closer, threading his fingers with Shiro’s as he pulled the prosthetic away from the face he loved. Shiro attempted to keep his expression blank, but Keith could read the smallest muscle movements. There was still a mental battle being fought. 

Keith took another step into Shiro’s space. He was playing with a dangerous fire, considering his own alpha nature. The long lines of his body grazed against Shiro, and he could feel where Shiro was half-hard already, just from a hint of that underlying scent. 

“You like that?” Keith pressed, his voice dropping husky and wanting, whispering the words into Shiro’s collarbone as he erased the space between their bodies. “Like the idea of an omega getting all slick for you?”

Shiro groaned, teeth bared and panting as he leaned harder against Keith, trying to maintain his control. Keith focused intently on Shiro’s breathing, the thrill of a potential rut piquing his own interest. “Keith,” Shiro finally managed, turning the name into a warning. But Keith’s caution was nearly derailed when he caught a quick flash of Shiro’s tongue against his upper lip, almost like he was trying to taste the lingering traces in the air.

Keith laughed under his breath, more at himself then at the situation. Shiro held him close, head finally turning to slowly nuzzle the crown of Keith’s head. Perversity drove Keith to continue to poke at that hormone-driven daze. “You want to breed an omega,” Keith breathed the words, cutting too close to the truth. The words felt so dirty, so contrary to Keith’s own nature. “You want to help scent a nest…” Keith paused to drag his tongue over Shiro’s scent gland, grazing it with his lower teeth. Teasing the promise of a bite. 

“Keith–” Shiro’s tone turned pleading, his fingers digging heavily into Keith’s biceps. An illicit thrill shivered down Keith’s spine. 

“Yeah? You want to make someone heavy with your pups?” Keith ran his hand down the front of Shiro’s body, feeling the tension thrumming beneath the muscles, the growing arousal that stopped Shiro from outright lying to him. “I can feel how much you want that…” he drawled lazily. A growl escaped from Shiro. 

Keith dragged his hands higher again, slipping underneath the edge of Shiro’s shirt as he pushed the material up. He purred at the feel of skin-on-skin, the warmth, the power underneath his fingertips. He leaned up on tiptoe, rubbing against Shiro’s neck, scenting him. “I want you to knot me,” he whispered, quietly, so close his lips grazed the delicate skin of Shiro’s ear. “I can take it. I want you to knot me, fill me like you–” he broke off, trailed his hand lower, trapping his fingertips in the tight waistband of Shiro’s pants. Shiro’s skin seemed hotter there, the texture of hair rough against the back of his knuckles as he tugged layers form fitting fabric away from Shiro. “You’ll knot, I know it,” Keith breathed, wanting it so badly. “Trust me to take it, Shiro,” Keith wavered between a demand and a plea. 

Shiro groaned. “Alphas aren’t made for that...” he dredged up his old protest. “Don’t want to hurt you.”

“You won’t,” Keith promised, so sure that he could take being so full, bringing his other hand to play as Shiro grew harder. “I’d tell you–”

“It’d be too late,” Shiro choked out, even as his body pressed pliantly into Keith’s hands.

“Shiro!” Old frustration bled into anger and Keith snarled.

The impact of his shoulder blades against the wall registered before he realized Shiro had thrown him backwards.

Startled more than anything, Keith jerked his arms up protectively, catching sight of the blown-wide pupils, an alpha just on the last edge of control. 

He tossed his chin up, answering the challenge in Shiro’s posture, and beckoned Shiro closer with a wicked grin. 

Barely a second later, Shiro hit the ground with a solid huff, wincing with the impact. For a moment he blinked, focusing on Keith and not the pheromones in the air. Keith’s lips curled into a small, prideful smile. 

Even if he didn’t have ‘typical’ responses there was some deep instinct in Keith that flared happily as he pushed Shiro down. 

With Shiro distracted, he had the upper hand. Keith grinned, sharp canines gleaming. “You make it too easy for me to take you down.” 

“Is that so?” There was a lazy, dangerous edge to Shiro’s smile that made Keith’s blood sing. Challenges always worked so well on Shiro in this state. 

Whatever twisted instincts made him crave this, crave knots, crave Shiro, pushed Keith closer to a proper rut too. 

Keith shoved his elbow into Shiro’s side when Shiro’s eyes slid down the hallway again. “Hey,” Keith snarled. “Look at me,” he demanded, throwing _power_ behind his voice.

Shiro’s attention snapped back to Keith, anger flaring in his expression, either at the tone or the way that Keith was posturing between him and the scent that he wanted. 

They erupted into another brief scuffle, settled by Keith spinning enough to get a knee onto Shiro’s arm, throwing his weight forward to lock Shiro into place. It took Shiro a moment of struggling before he accepted he was pinned again. 

Chest to chest, Keith could tell that their heartbeats were both raised. That didn’t change as the aggressive tension bled into something more mellow. Keith lazily shifted so that he was pressed against Shiro’s side more tenderly, pushing one of his legs between Shiro’s. He traced a finger down Shiro’s chest. Lower. 

“You can imagine it, right?” Keith purred. It irritated him, the way Shiro’s attention could be drawn somewhere else. He wanted to do something to change that. “You want something tight around your knot?” He stroked the base of Shiro’s cock, gently pulsing his fingers around it. With Shiro pinned underneath him it was easy to feel almost drunk on power. 

Shiro’s body trembled, lust playing against anger at being denied the omegas. “We should take this somewhere else…” Shiro murmured, and Keith’s grin widened. Keith stood, offering a hand to pull Shiro up after him.

“Still…. the hallway would be kind of hot…” Keith teased under his breath. 

Shiro pressed a steadier kiss into Keith’s forehead, more like himself for a moment. “Do you ever run out of kinks?” Shiro asked, all playfulness and raised eyebrows. “Could we maybe just take them one at a time?”

Keith just grinned, shoulder-checking Shiro as he passed. 

They barely made it to Keith’s quarters.

* * *

Keith groaned something that might have been Shiro’s name as he flinched. It was muffled by the end of his black t-shirt, caught between his teeth to keep it out of the way. 

Shiro laughed from behind Keith. “A little cold?” he asked, too innocently. 

Keith growled against the shirt, careful not to move too much as he leaned forward, resting his forehead on his crossed forearms against the wall. His pants had been roughly shoved down to his ankles, trapped by his boots, and he was terrified to fall over if he tried to move too much.

The cool liquid spilled across his lower back. Too much. Waaaay too much. He shivered as it ran down his body.

“Gonna make you so messy for me,” Shiro promised, and Keith felt him kneel behind him.  
Well. He _had_ teased Shiro before.

More fingers, everything growing slick and wet. Shiro’s fingers were light against his balls, tickling as he played with the slick liquid before stroking upwards. Keith clenched involuntarily.

Keith gritted fabric between his teeth, growing wet with saliva.

The back of Shiro's knuckles caressed him, following up his taint with teasingly-light pressure, to push more of the lube into the skin around his tight entrance. "You ready to start?" Shiro asked huskily.

Keith nodded, his yes drowned in soggy fabric. He struggled to shift his feet a little wider, trapped by his own pants. He shivered as he felt two thumbs trace upwards, fingers fanning out on both of his cheeks, spreading them slightly, the slip of the lube dulling the contrasting textures of Shiro’s hands.

Shiro's thumbs met at his asshole, one massaging the surface in tight, overlapping circles. Hot breath tickled for a moment as Shiro lapped between them, tongue velvety over the lube and tight skin.

Keith let his head fall backwards and he groaned as Shiro started to rim him. Shiro's lips made a sloppy seal over the area, and Keith's legs nearly bowed when Shiro started to tease him with the point of his tongue rather than flat lazy strokes.

Every touch made Keith practically vibrate with contained pleasure. When Shiro pulled back Keith was gasping.

One of Shiro's hands forced its way between Keith's legs, wrapping around Keith's cock with a lazy familiarity and pumping a few times. "You're so hard, babe," Shiro murmured. "You like when I do this?"

Keith shut his eyes and tried to regain his breathing. He did make a disappointed keen when Shiro’s hand drew back through his thighs, separating his cheeks slightly with commanding pressure. 

Feeling exposed, Keith shifted his weight, uncomfortable with the pause.

Shiro stood up, leaned in close over him. He could feel Shiro's chin, slick against his shoulder. "You're all sloppy and wet, bet you can't wait to take me..." Shiro whispered. He bit down on Keith's scent gland as he curled one finger into his body, pushing past the first tight ring of resistance. Keith moaned at the combination of pain and pleasure.

"Can feel you, you're so tight, so tight around me." Shiro groaned into the mark he was making. It took a moment for Keith to relax under Shiro, all his concentration first latching onto just how good it felt to have Shiro suck bruises into his skin. The heat and pleasure blurred the sharp sting of pain.

"Mmm," Keith tried to make an agreeable noise. Shiro shifted, moved back, and drizzled more lube over Keith's backside, twisting his finger and making Keith practically purr in pleasure when he pushed in a second with slick rivulets of lube. Shiro stroked Keith's chest, pinching at his nipples, barely exposed by the rucked up shirt. He knew it was meant as a distraction; but every movement of Shiro's fingers across his chest were bliss. When Shiro pinched, the sharp pain exploded with pleasure, throbbing heat travelling straight to his groin.

"So tight babe," Shiro teased. "Maybe you've been topping too much. Maybe you aren't prepared enough for me..."

Keith made a noise of pure despair.

Shiro laughed. "So greedy for everything."

Keith's internal muscles kept testing the fingers in him, especially as Shiro began to move them. Keith's hips slowly rocked with the movement, getting used to the sensation and slowly relaxing enough that the press became pleasurable. Shiro shifted, twisting his wrist enough that he could hook his fingers down and forwards.

Keith's eyes nearly rolled back in his head as Shiro stroked over his prostate.

"Ready for more?" 

Keith nodded enthusiastically.

"Bed?" Shiro asked.

Keith nodded his agreement again, wincing at the sensation as Shiro pulled out. 

Keith made it as far as carefully turning before he collapsed back against the wall, a little unsteady as he stripped off his shirt. Shiro knelt to help with Keith's boots.

"You look good like that," Keith teased the alpha at his feet.

Shiro's wicked grin said he knew that too, and he leaned forward enough to very deliberately lick up the trail of precum leaking from the tip of Keith's cock. "Maybe you want this instead?"

Keith shook his head fondly. "Can't distract me this time." He ran a hand through Shiro's hair, pulling him back with a sharp tug and a gentle grin. Through the intervention of a minor miracle they managed to rid themselves of the rest of their clothes.

"So uh, how..." Keith gestured, looking to Shiro for guidance. Shiro had knotted others before.

"I want to see your face," Shiro said roughly. "Don't hide it if it starts to hurt, I can probably pull out before we're really locked..."

Keith winced, fear briefly edging into his thoughts despite his determination. He sprawled backwards onto the bed, pulling Shiro’s hips closer. He ran his hand across to Shiro’s cock, toying with the slightly puffier areas that would flare into a full-blown knot. "I want it," he reaffirmed.

Shiro gave a half smile and pushed Keith down. He knelt between Keith's splayed legs. stroking his own dick, the lube making slick, slippery noises as he covered himself too.

"I think that might be enough," Keith said dryly, eyebrow raised. 

Shiro managed to look a bit abashed. He inched forward on the bed, sliding one hand up the inside of Keith's leg, catching the underside of his knee and pushing it up towards Keith's shoulder.

Keith hissed at being so exposed, although it had no effect on his hard-on, drooling over his stomach.

Shiro didn’t move fast enough. "I can show you how this is done if you want..." Keith growled from behind gritted teeth, the anticipation clawing at his sense of self control.

Shiro smirked as he pressed forward. Keith's free leg skidded across the sheets. His back tightened like a bowstring and he gasped. Shiro slipped in slowly, eventually removing his steadying hand and using it to pull Keith's other leg up. He slowly drove deeper.

"C'mon Takashi," Keith panted as he got used to Shiro's length. "Show me what you wanted to do when you smelled their heat..." He writhed underneath, but Shiro was still so in control.

Shiro bit his lower lip, so Keith continued. "Show me what you'd do to a heat-slick omega, be rough, I can handle it...."

A shudder ran through Shiro that Keith could feel. Shiro began to move, still so carefully, still testing. Keith made contented noises and let his body move with the force of Shiro's thrusts. "Like that, Takashi," he whispered. "Harder." Shiro was already so thick, and Keith's alpha body was so tight around him. "You feel perfect," Keith promised, reaching up to tangle his hands behind Shiro's head. 

It didn’t take too long. “Oh god,” Keith rocked a bit. “I think I can… Takashi?”

Shiro nodded, face betraying his immense concentration. “It’s starting.”

Keith clenched experimentally.

Shiro shivered and sank forward, leaving no room between them. He held Keith close as his knot began to swell further. 

Keith luxuriated in the feeling of it growing inside him. The knot was sealed firmly inside him, not stretching his rim so much but… oh. Just so big. It felt like it was everywhere inside. 

Shiro began to grind, slow and steady. Each movement pushed the thick flesh into Keith. Keith arched his back. “ _Fuck,_ yes!” he whispered. 

The knot grew firmer, becoming a steadier pressure and at each gentle rock a familiar feeling started welling up.

“Oh yes,” Keith mumbled encouragement as his orgasm loomed nearer. 

“Keith,” Shiro nuzzled into his neck, unable to manage more than his name. 

Keith toes curled, and when Shiro let go of his legs he locked their shaky lengths around Shiro’s hips, clamping them together. His cock twitched as the blissful pressure continued to grow, heavy and unrelenting. 

“Takashi… I’m gunna….” Keith’s face wrinkled into a grimace as he spilled between them. 

The contractions around Shiro were enough to tip him over the edge too, and Keith felt his insides flood with heat. 

He struggled to reign back his pounding heart. Sharp edges slowly reappeared in his hazy vision. The lingering sense of fullness was strange, but not unpleasant. 

Shiro maneuvered them gently into lying on their sides. Keith stroked a hand across Shiro’s jaw, still feeling slightly lightheaded. “Thanks,” he murmured sleepily. 

Shiro laughed and scrubbed a hand over his face. “I can’t believe....” he whispered, shaking his head as he reached down to feel at where they were joined. “You’re ok?”

“Yeah... “ Keith opened his eyes lazily, leaning forward to kiss Shiro lightly. “Felt good. Feels good.” He smiled a little too contentedly. It was a bit of a risk… but… Keith shrugged, and shut his eyes. 

“I told you so.”

**Author's Note:**

> * * *
> 
> I’ll have a different omegaverse story “Hollow Horses” in the zine itself! You can follow the progress of the Zine on [Tumblr](https://abovoltronzine.tumblr.com/%20) or [Twitter](https://twitter.com/ABOVoltronZine).
> 
> (And you can find me on [Twitter](https://twitter.com/HerPaintstrokes). <3 Thanks for reading!)
> 
> * * *


End file.
